We begin with the promise of action in the w of tragedy. President obama saying today he will use all the powers of his office to help americans work together to end an epidemic of gun violence in this country. So, what will the president do first? Abc's jake tapper was there and questioned the president today. Jake? Reporter: Good evening, diane. After years of what critics charge has been not much discussion and even less action on the issue of addressing gun violence, today, president obama said that the tragedy at sandy hook changed everything, and now focusing on these issues will be at the forefront of his agenda. The president promised action. I will use all the powers of this office to help advance efforts aimed at preventing more tragedies like this. We won't prevent them all, but that can't be an excuse not to try. Reporter: He pledged that his administration would look at the mental health, education, cultural and gun control aspects of this tragedy. And to head the effort, he appointed vice president biden, an you a thundershower of the 1994 crime bill, which contained a ban on some semiautomatic rifles. The team will report back by next month, he said. The president looks to capitalize on this moment, when even some pro-gun rights democrats are looking for change. Closing the so-called gun-show loophole that does not require background checks in many private sales. And ban the sale of what he called military-style all weapons. If we're going to change things, it's going to take a wave of americans, mothers and fathers, daughters and sons, pastors, law enforcement, mental health professionals, and yes, gun owners standing up and saying, "enough," on behalf of our kids. Reporter: The white house vaguely defines military-style assault weapons as those that can fire hundreds of rounds in minutes. For perspective, this is an m-16 automatic rifle. It's generally illegal to the public. It can fire continuously. With one pull of the trigger, the bullets come nonstop. 30 rounds in two seconds. This gun, an ar-15 style rifle, is legal. And very popular. It looks similar to an m-16 on the outside, but it's semiautomatic. One bullet gets fired per pull of the trigger. This takes 10 to 15 seconds to fire off 30 rounds. And tomorrow, vice president biden will meet with law enforcement officers from all across the country to talk about next steps. We should point out that the fraternal order of police supporting reinstating that ban on some semiautomatic rifles, which vice president biden wrote in 1994, but it expired in 2004.

This transcript has been automatically generated and may not be 100% accurate.

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